Conductive Direct Metal Bonding via Oxide Mediator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing direct conductive metallic bonding techniques for semiconductor substrates are constrained by surface preparation requirements, contamination risks, and temperature limitations, leading to defects and reduced electrical conductivity.
Innovation Solution
A method involving direct contact between metal oxides formed at the bonding interface, which enhances bonding energy and allows for improved electrical conduction, mechanical strength, and reduced surface preparation constraints, using controlled oxidation and thermocompression to achieve high-quality bonding without damaging components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If direct metallic bonding is performed without thermocompression, then surface preparation constraints are severe (roughness ≤0.5 nm RMS, high hydrophilicity required), but bonding energy is insufficient and interface quality is poor
Solution Approach 1:
A metal oxide layer is introduced as an intermediary substance between the two metal surfaces to be bonded. This oxide layer facilitates bonding at lower temperatures by enabling chemical reactions that form strong interfacial bonds, thereby resolving the contradiction between low bonding temperature and stringent surface preparation requirements.
Solution Approach 2:
The chemical composition of the bonding interface is changed from pure metal-metal contact to metal-oxide-metal contact. This parameter change allows bonding to proceed under milder conditions with relaxed surface roughness constraints, as the oxide layer provides a more tolerant bonding interface.
2Manufacturing precision
If thermocompression is applied to assist copper bonding, then surface preparation constraints are relaxed (roughness up to 8.6 nm RMS feasible), but process temperatures ≥350°C can damage components on the structure
Solution Approach 1:
The metal oxide serves as a mediator that enables effective bonding without requiring the high temperatures of thermocompression. The oxide facilitates chemical bonding at lower temperatures while still accommodating higher surface roughness, thus resolving the contradiction between temperature sensitivity and surface tolerance.
3Reliability
If conventional direct bonding is performed between metals, then bonding interface is formed, but voids appear at the interface limited by grain boundaries reducing reliability
Solution Approach 1:
The metal oxide layer acts as a mediator that fills and seals the voids that would normally form at the metal-metal interface. By providing a compliant and reactive intermediate layer, it prevents void formation and grain boundary limited defects, thereby improving interface quality and reliability.
4Manufacturing precision
If metal surfaces are highly polished to achieve roughness ≤0.5 nm RMS, then direct metallic bonding quality is improved, but material is consumed and processing time increases
Solution Approach 1:
The bonding mechanism is changed from direct metal-metal contact requiring ultra-smooth surfaces to metal-oxide-metal contact that tolerates higher roughness. This parameter change in the bonding interface composition dramatically reduces the time and material investment required for surface preparation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves enhanced bonding energy, improved electrical conductivity, and reduced material consumption, enabling bonding with higher surface roughness and relaxed hydrophilicity requirements, while minimizing thermal stress on substrates.
Implementation Method 1
the metal oxide formed at the bonding interface makes it possible to generate metal/oxide/metal contact zones at the level of the cavities, thus reinforcing the bonding energy
Implementation Method 2
Annealing can then be applied to the structure in order to reinforce the quality of the bonding. At the end of this heat treatment, the bonding interface appears reconstructed
Implementation Method 3
an additional supply of energy is provided at the time of the bonding of the substrates in calorific and mechanical form by the application of pressure on either side of the assembly
Data Source
Figure 1~5
AI summary
The invention comprises the steps of -a) Providing a first substrate (1) covered by a metal layer (2) and a second substrate (3) covered by a metal layer (4), -b) Bringing the metal layers (2, 4) into direct contact in such a way as to form a bonding interface (6) comprising metal material bridges (5) separated by cavities fluidly connected together, -d) Submerging the bonding interface (6) in an oxidising fluid (8) in such a way as to form a metal oxide at least partially filling the cavities and metal/metal oxide/metal contact areas (9). The invention also concerns a structure (100) comprising a first substrate (1), a first metal layer (2), a second metal layer (4) forming a bonding interface (6) with the first metal layer (2), and a second substrate (3), the bonding interface (6) comprising metal material bridges (5) separated by cavities, a metal oxide at least partially filling the cavities and metal/metal oxide/metal contact areas (9).